Steam has been used in many different methods for the recovery of oil from subterranean, viscous oil-containing formations. The two most basic processes using steam for the recovery of oil includes a "steam drive" process and a "huff and puff" steam process. Steam drive involves injecting steam through an injection well into a formation. Upon entering the formation, the heat transferred to the formation by the steam lowers the viscosity of the formation oil, thereby improving its mobility. In addition, the continued injection of the steam provides the drive to displace the oil toward a production well from which it is produced. Huff and puff involves injecting steam into a formation through an injection well, stopping the injection of steam, permitting the formation to soak and then back producing oil through the original injection well.
U.S. Pat. No. 4,109,722 to Widnyer et al, discloses a method for injecting steam into a subterranean viscous oil-containing formation by a single well push-pull method in which steam injection and oil production occurs in the same well using a pressure pulsing technique to stimulate production at greater distances in the formation. In Widnyer et al, one well is drilled through the entire viscous oil formation and completed so as to establish two separate communication paths between the surface of the earth and the lower and upper portion of the formation. Initially, steam is injected into the lower and upper portion of the formation via both flow paths for a period of time followed by a soak period if desired followed by production of heated oil from both parts of the formation. Thereafter, steam is injected into either the upper or lower portion of the formation, and oil is produced from the other portion. The injection-production sequences are then reversed.
One of the problems associated with steam assisted oil recovery is that if steam stimulation is used, production is discontinued during the injection phase and if steam flooding is used, obtaining and maintaining a warm producing well can be difficult. I have found a means of combining steam stimulation with steam flooding using a single wellbore that enhances oil recovery by maximum gravity drive displacement of the oil.